Option ROM and I/O Space Allocation

Bootable devices such as onboard I/O or PCIe express modules require option ROM
and I/O space to boot. However the total option ROM and I/O
space for the system is limited by the PC architecture and is allocated
automatically when the system is booted. If your system includes many potentially bootable devices,
you must decide which ones you wish to boot from, and configure
the BIOS to allocate these resources to them.

Option ROM is also required to run some configuration utilities, such as the
LSI RAID configuration utility. This utility, which resides in the REM, has option
ROM and I/O space allocated to it by default.